Researchers at Boston's Dana-Farber Cancer Institute managed to reverse brain disease and restore fertility and the sense of smell in prematurely aged mice, using a gene therapy technique.

The aging process shortens coatings on the ends of chromosomes, called telomeres, causing cells to stop dividing, stem cells to hibernate, brain cells to die and organs to atrophy. By restoring the telomeres in the mice, scientists were able to halt these processes, according to a study published in the journal Nature.

"These mice were equivalent to 80-year-old humans and were about to pass away," Dr. Ronald DePinho, co-author of the paper and a scientist at Dana-Farber, told the Wall Street Journal. After the experiment, "they were the physiological equivalent of young adults."

The mice, which the researchers genetically engineered to age prematurely, had atrophied spleens, damaged intestines and impaired senses of smell. Their brains were shrunken and incapable of growing new cells and the male mice had shrunken testes and low sperm counts.

"We stacked the deck against us and asked, 'Is there a point of no return?'" DePinho told the Journal.

A month after scientists gave the mice an estrogen-based compound to reactivate the dormant telomerase gene, their brains were producing new cells and their spleens, testes and brains all grew. Key organs showed improved function, as did the sense of smell. The mice went on to live a normal lifespan.

The study is only a first step toward a similar treatment for humans. One risk is cancer; tumors have been shown to reactivate the telomerase gene, allowing their cells to reproduce themselves. DePinho told the newspaper that the next step is to try the technique on normally aged mice to determine whether similar results can be achieved.

Scientists in Boston have made an astounding discovery, taking aging mice and turning them young again, like tiny little Benjamin Buttons.

Just like the title character in the Hollywood film version of "The Curious Case of Benjamin Button," the mice appeared to not only stop aging but grow younger.

Molecular biologist Dr. Ronald DePinho at Harvard Medical School in Boston was able to pull off the feat by playing with "telomeres" -- the protective DNA caps on the ends of our chromosomes.

The caps, which have long been implicated in aging, prevent our chromosomes from "fraying" and the genes inside them from "unravelling."

Scientists have long known that a little bit of our telomeres erodes each time our cells divide. Previous research has shown that people with longer telomeres tend to live longer, whereas those with shorter telomeres suffer more from age-related diseases, such as Alzheimer's.

A few years ago, DePinho and his research team devised a way to engineer mice so that they lacked a working copy of the gene that regulates the production of telomerase, which is an enzyme that strengthens telomeres and whose production declines over time.

Instead of dying at three years old, the genetically engineered mice died at about six months. By the time they died, they had become infertile, their coat hair had turned grey and they had developed age-related conditions such as osteoporosis.

DePinho wondered whether he could reverse the aging in the mice if they suddenly began making telomerase again.

So he took a group of engineered mice and added back the telomerase gene, but left it inactive. His team then allowed the mice to age for six months, until they were the equivalent of 80-year-old humans. They then gave the mice a drug that "switched on" the telomerase gene.

One month later, not only did the new production of telomerase stop the aging process in the mice, it appeared to actually undo the premature aging so that the mice became the physiological equivalent of young adults.

Even DePinho was surprised at how effective the experiment was.

"We expected to see a slowing or a stabilization of aging. Instead, what we found was a dramatic reversal in aging," he told CTV.

"The shrunken brains increased, new neurons were formed, the coat hair was restored to a new sheen."

DePinho notes that the treated mice went on to have a normal lifespan. They were simply healthier and biologically younger.

DePinto and his colleagues stress that the study was a "proof-of-concept" experiment, designed to show that changes to telomerase can affect aging. There are still many questions to answer before an experiment can be tried on humans.

For example, some research has shown that telomerase seems to help cancer tumours grow faster. DePinho says his team didn't observe any cancers in the mice, but then the telomerase was activated for only one month.

"This teaches us something fundamental about aging: that aged tissue -- even very aged tissue -- retains the ability to rejuvenate itself," he said.

DePinho says it's possible the method could be used to treat people with rare genetic premature aging syndromes. Whether the technique could help reverse normal aging still remains to be seen. Still, he says the findings were worth sharing and appear in the journal Nature.

"The results were so dramatic that we wanted to get them out to the research community as soon as possible so we could inspire the research community to move forward on these findings," DePinho said.